1. Field of the Invention
The present invention relates to an a.c. generator for a vehicle, which is driven by an internal combustion engine of the vehicle, and a method of producing the a.c. generator.
2. Discussion of Background
FIG. 12 is a cross-sectional view of an example of generally used a.c. generators for vehicles, which is disclosed in Japanese Unexamined Patent Publication JP-A-2000-50553. In the figure, a rotator 1 has a rotating shaft 11, a pair of field iron cores 12 of a Randle type, engaged with the rotating shaft 11, and a field winding 13, fixed to the field iron cores 12. The rotating shaft 11 is rotated by receiving a driving force by the internal combustion engine of the vehicle through a belt (not shown).
A stator 2 surrounding the rotator 1 has a stator iron core 21 and a group of stator windings 22, fixed to the stator iron core 21. An inner peripheral surface of the stator 2 is arranged opposite to an outer peripheral surface of the rotator 1 through a gap. Further, the stator 2 is interposed and held between a front bracket 31 and a rear bracket 32.
In the next, the stator 2 will be described in detail. FIG. 13 is a perspective view of a conductor segment, forming the group of the stator windings 22, wherein a state before building this in the stator iron core 21 is shown. In the figure, the conductor segment 23 is formed by bending a rod-like or plate-like metallic material, e.g. copper, at a bent portion 23c so as to be substantially U-like shape. The conductor segment 23 has a conductor 23a on an inner layer side, arranged on a side of a slot inner than the bent portion 23, and a conductor 23b on an outer layer side, arranged on a side of a slot outer than the bent portion 23.
FIG. 14 is a cross-sectional view of a part of the stator iron core 21. FIG. 15 is a perspective view of party illustrating a state that the windings are inserted in the stator iron core 21. The group of the stator windings 22 is formed by inserting two pieces of the conductor segments 23 respectively into each one of the slots 24 of the stator iron core 21, and by mutually shaping end portions 23d of the conductor segments, which were inserted in different slots 24, as illustrated in FIG. 15. An insulating coating is respectively formed on surfaces of the conductor segments 23, and therefore adjacent conductor segments 23 are insulated each other by the insulating coatings. Further, each of the conductor segments 23 is insulated from a corresponding inner wall surface of the slot 24 by a tissue paper 25.
FIGS. 16 through 18 illustrate a method of producing the stator winding, wherein the tissue paper 25 is omitted. The tissue paper 25 is shaped like a ring sufficient for one slot, and inserted in the slot along an axial direction of the slot 24. After building the tissue paper 25 in the slot 24, the conductor segment is inserted in the slots 24 along the axial direction, as arrows A in FIG. 16. The inserted conductor segment 23 protrudes from the other side surface of the slot 24 at an end portions 23d, and the end portions 23d are bent in peripheral directions of the stator iron core 21 as arrows B, i.e. twist shaping, to connect another end portion 23d of a conductor segment 23, inserted in a different slot 24.
However, there are problems in the conventional a.c. generator for the vehicle that a material cost of the tissue paper 25 is required because the conductor segments are insulated from the stator iron core 21 by the tissue paper 25, the number of steps in manufacturing the a.c. generator is increased, and therefore a cost is increased.
Further, as illustrated in FIG. 16, when the conductor segment 23 is inserted in the directions of the arrows A into the slots 24 of the stator iron core 21 and when the conductor segment 23 is bent in the directions of the arrows B at a time of twist-shaping as illustrated in FIG. 17, the tissue paper 25 and the insulating coating of the conductor segment 23 are peeled off by a contact between an opening edge of the stator iron core 21 on the end surface 27 and the conductor segment 23, whereby a resistance to voltage is deteriorated.
Further, as illustrated in FIG. 17, when the conductor segment 23 is bent in the directions of the arrows B at the time of twist-shaping, an excessive stress is applied to the end portion 27 of the stator iron core 21, whereby there are problems that laminated steel plates forming teeth 28 are deformed and shifted in peripheral directions on an inner diameter side of the stator iron core 21, a magnetic circuit is affected, and therefore an output voltage is decreased.
Further, although the tissue papers 25 are interposed between the stator iron core 21 and the conductor segments 23, gaps still exist between inner wall surfaces of the slots 24 and the tissue papers 25. Therefore, there is a problem that a quality of the a.c. generator for vehicle is deteriorated by a shift of the conductor segment 23 at a time of inserting this, insufficient insulation caused by intrusion of moisture into the gaps, and deterioration of heat conductivity (cooling capability) between the conductor segments 23 as electric heating elements and the stator iron core 21.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an a.c. generator for a vehicle which has high insulating and cooling capabilities of a stator, is easily manufactured, has a high quality, and is produced at a low cost, and also to provide a method of manufacturing the a.c. generator.
According to a first aspect of the present invention, there is provided an a.c. generator for a vehicle comprising: a rotator; a stator iron core arranged opposite to an outer periphery of the rotator and having a plurality of slots; and a stator including a plurality of conductor segments, which are accommodated in the slots to form a stator winding, wherein the stator iron core is insulated from the conductor segments by coating at least an end surface of the stator iron core and an inner wall surfaces of the slots with an insulating resin.
According to a second aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the insulative resin is formed around opening edges of the slots on sides of the end surfaces of the stator iron core so as to be in a rounded shape or a chamfered shape.
According to a third advantage of the present invention, there is provided the a.c. generator for the vehicle, wherein the stator iron core is formed to be in a rounded shape or a chamfered shape around opening edges of the slots on sides of the end surfaces of the iron core.
According to a fourth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the insulative resin is made thicker at around opening edges of the slots on sides of the end surfaces of the stator iron core than at center portions of the slots in their axial directions.
According to a fifth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the conductor segments have a substantially rectangular cross-sectional shape.
According to a sixth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the end surfaces of the stator iron core are shaped to be uneven.
According to a seventh aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the inner wall surfaces of the slots are shaped to be uneven.
According to an eighth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the insulative resin has a breaking strength sufficient to withstand breakage, caused at a time of inserting the conductor segments into the slots.
According to a ninth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the insulative resin includes silicone.
According to a tenth aspect of the present invention, there is provided the a.c. generator for the vehicle, wherein the insulative resin includes epoxy.
According to an eleventh aspect of the present invention, there is provided a method of manufacturing an a.c. generator for a vehicle comprising steps of: forming a stator iron core by laminating annular steel sheets, in which a shape of slots is punched out; and coating at least inner wall surfaces of the slots and end surfaces of the stator iron core from axial directions of the stator iron core with an insulative resin.
According to a twelfth aspect of the present inventions, there is provided the method of manufacturing the a.c. generator for the vehicle, wherein the coating of the insulative resin is provided by electrostatic powder coating.